Resumo

INTRODUCTION: Species of Candida are the most important cause of mycoses worldwide. Emerging fungi as Cryptococcus spp., Trichosporon spp., Geotrichum spp., and Rhodotorula spp. are also significant due to their virulence and resistance to the majority of drugs available for treatment. Plants of the Hypericum genus are a notable source of new therapeutic agents and several species are used in traditional medicine. This study reports the antifungal activitiy of the lipophilic extracts of five Hypericum species (H. caprifoliatum, H. carinatum, H. linoides, H. myrianthum and H. polyanthemum) native to South Brazil. MATERIALS AND METHODS: It was tested the antifungal activity (500μg/mL) of the five extracts against 11 species of pathogenic yeasts. The Hypericum species whose extract showed high inhibition percentage were selected for the determination of minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC). Tests were performed using the broth microdilution assay according to M27-A3 documents determined by the Clinical Laboratory and Standards Institute (CLSI). DISCUSSION OF RESULTS: All samples exhibited a broad spectrum of antifungal action. C. neoformans and R. mucilaginosa were the more susceptible yeasts. Regarding these pathogens, the extracts of H. carinatum, H. linoides and H. myrianthum presented values MIC ≤ 15.6 µg/mL and MIC ≤ 62.5 µg/mL, respectively. In addition, H. myrianthum extract also displayed the lowest value of MFC (7.8 – 15.6 µg/mL) against R. mucilaginosa. Within the Candida genus, the most sensitive species were C. glabrata and C. tropicalis with MIC values varied in the range of 1.9-250 µg/mL for both the extracts above mentioned. The observed effects could be attributed to the phloroglucinol derivatives, compounds present in the investigated extracts. CONCLUSION: The Hypericum species from South Brazil confirm their potential as source of new antimicrobial drugs. In the future, the biological activity of the isolated compounds will be investigated in order to confirm the impressions of this study as well as to determine their mechanism of action.